The invention concerns a stopping device for a crop transport or feed mechanism of a harvesting machine with a movable detent, which is set up to assume a first position in which the crop transport mechanism is stopped and a second position in which the crop transport mechanism is movable, and with a device to move the detent.
In the prior art, forage choppers were equipped with metal detectors set up to detect undesired metal objects, especially ferromagnetic objects, that have entered the chopper, If such an object is detected, a detent is triggered by a control which stops a draw-in roller and engages a connected out-of-round element to rotate in unison with it especially a cam. At the same time the drive of the draw-in roller is disengaged. The detent is brought from a blocking position, hereafter called the first position, against the action of a spring, to a second position in which the draw-in roller is rotatable by a control connected to the metal detector by means of an electromagnetic drive, generally an electromagnet. This type of forage chopper is known, for example, from EP 0 324 253 A and DE 2 552 805 A.
The electromagnetic drive in the known forage choppers is always activated when a normal work operation occurs, and the detent is therefore in the second position. In order to achieve the situation by which the draw-in roller is stopped sufficiently quickly after detection of a metal object, a correspondingly strong spring must be used that brings the detent back to the first position quickly enough after disengagement of the electromagnetic drive. The electromagnet must be sufficiently large in dimension to overcome the force of the spring, and this feature loads the electrical system of the harvesting machine quite severely because of the relatively high current necessary for its operation. Nevertheless, it is problematical whether a sufficiently short time interval for stopping the draw-in roller is achievable. Moreover, because of the quite limited holding force of the electromagnet caused by the relatively high current demand, the detent can fall onto the cam, especially when the harvesting machine passes over a ground depression, and thus cause an unintentional stop of the draw-in roller. This incorrect function is called false tripping.
A protective system for an agricultural harvesting machine is proposed in U.S. Pat. No. 3,805,497 in which a detector for obstacles controls a valve by which a hydraulic cylinder can be charged with pressurized fluid. The hydraulic cylinder lifts the draw-in devices of the harvesting machine if an obstacle is detected in order to protect them from damage.
The problem underlying this invention, in addition to the problem of false tripping and the relatively high current demand of the known devices for stopping crop transport mechanisms of a harvesting machine, is seen in the fact that the disconnection times are not always sufficient to protect the chopping drum from damage.
According to the present invention there is provided an improved stopping device for the crop feed of a forage harvester.
An object of the invention is to provide a stopping device for the crop feed of a crop harvester which reliably functions only in response to a metal detector signal.
A further object of the invention is to provide a stopping device for the crop feed of a crop harvester which operates such that the stopping device acts to block crop feed operation when there is a loss of power for energizing a control of the stopping device.
A more specific object of the invention is to provide a stopping device, as set forth in one of the previous objects, wherein a detent for engaging a toothed wheel coupled to a rotary crop feed element is controlled by a one-way hydraulic cylinder and a coil tension spring coupled in parallel with the cylinder and such that, when pressurized, the hydraulic cylinder acts to engage the detent with the toothed wheel, and when the hydraulic cylinder is coupled to sump, the spring moves the detent out of contact with the toothed wheel.
These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings.